In article <E176GHv-0006ee-00@the-village.bc.nu>,
Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
>> kernel. It would be possible to allow program access to this RAM, although
>> both Kernel and gcc support would be needed. M$ had "huge" memory models
>> to go over 64k in the old 8086 days, doing loads of segment registers.
>
>Alas that is not quite the case. You still have a 4Gb virtual address
>space. If you want > 32bits, get a > 32bit processor. This one isnt as
>simple as add segmentation and 'large model'
Well, you _could_ use the P bit on the segments and "page" them in on
demand with mmap. That would get you a model very similar to the old
16-big large model: no single object can be bigger than 2GB, but you can
have a total object size of something like 40 bits.
No kernel support needed, actually. It's all there with the LDT stuff.
But yes, compiler support and a recompiled glibc. And it would break all
programs that assume a flat address space.
And it would really _suck_ performance-wise if your working set is big
enough to cause you to have to switch mmap's a lot.
Linus
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This archive was generated by hypermail 2b29 : Tue May 14 2002 - 12:00:14 EST